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What’s new in oral cavity and oropharyngeal cancer research and treatment?

Important research into oral and oropharyngeal cancers is taking place in many university hospitals, medical centers, and other institutions around the country. Each year, scientists find out more about what causes the disease, how to prevent it, and how to improve treatment.

DNA changes

A great deal of research is being done to learn what DNA changes cause the cells of the oral cavity and oropharynx to become cancerous.

One of the changes often found in DNA of oral cancer cells is a mutation of the TP53 gene. The protein produced by this gene (called p53) normally works to prevent cells from growing too much and helps to destroy cells with too much damage for the cells to repair. Changes in the TP53 gene can lead to increased growth of abnormal cells and formation of cancers. Some studies suggest that tests to detect these gene changes may allow oral and oropharyngeal tumors to be found early. These tests may also be used to better find cancer cells that may have been left behind after the tumor is removed and to determine which tumors are most likely to respond to surgery or radiation therapy.

Another DNA change found in some oropharyngeal cancer cells (and less often in oral cancer cells) is the presence of DNA from a human papilloma virus (HPV). Some parts of the HPV DNA instruct the cells to make proteins that inactivate the p53 protein, which may allow the cancer cells to grow and divide. Studies are looking at whether tests to detect HPV DNA could help diagnose these cancers.

In addition, most studies suggest that oropharyngeal cancers that are linked with HPV tend to have a better outcome than those without HPV. Studies are being done to see if HPV-linked cancers can be treated less aggressively without reducing survival. Researchers are also working on treatments aimed at HPV infections or that target HPV-infected cancer cells.

So far, studies using isotretinoin (13-cis-retinoic acid) and other drugs related to vitamin A (retinoids) have not found any long-term benefit in helping patients avoid cancer or live longer.

Several other types of drugs are now being tested to help prevent these cancers. Non-steroidal anti-inflammatory drugs (NSAIDs), such as sulindac and celecoxib are being tested as chemopreventive drugs. Erlotinib (Tarceva®), a drug that blocks the epidermal growth factor receptor (EGFR) from signaling cells to grow, is also being tested for chemoprevention of head and neck cancers. Some early research has found that certain extracts of black raspberries may help prevent these cancers. Another compound showing some promise is known as Bowman-Birk inhibitor (BBI), a protein derived from soybeans.

All of these drugs and compounds would need further study before they could be recommended.

Treatment

HPV related cancers

Because cancers linked to the HPV virus seem to behave differently from other oral cavity and oropharyngeal cancers, they are being studied separately in some clinical trials.

Surgery

Doctors continue to refine surgery techniques to try to limit the amount of normal tissue that is removed along with the tumor. This may help limit the side effects after treatment.

Sentinel lymph node mapping and biopsy: In many oral cancers, the nearby lymph nodes are routinely removed during surgery (known as a lymph node dissection). A sentinel lymph node biopsy can help the doctor determine whether the cancer has spread to these nodes beforehand, which may allow the patient to avoid this surgery if the cancer has not spread. Sentinel node mapping and biopsy helps the doctor identify and examine the sentinel node(s) — the one(s) that the cancer would have spread to first before it went to other nodes. If this node doesn’t contain cancer, it’s very unlikely that any other nodes would contain cancer either.

In this procedure, the surgeon injects a radioactive material around the tumor, usually the day before surgery. The material will travel the same route that any cancer cells would likely have taken if they went to the lymph nodes. On the day of surgery a blue dye is injected into the tumor site, which will also travel to the nearby lymph nodes.

During surgery, the surgeon can use a radiation detector to find the lymph node region that the radioactivity (and presumably the cancer) may have spread to. The surgeon then cuts into the area to look for radioactive or blue stained lymph nodes. These are removed and examined by a pathologist. If there is no cancer, then no further surgery is needed. If there is cancer, then all the lymph nodes in the area will be removed.

Most doctors still consider this procedure to be experimental for cancers of the mouth and throat, and more work is needed to tell if this can replace routine lymph node removals.

New chemotherapy approaches

A great deal of research is focusing on improving results from chemotherapy (chemo) in people with these cancers. This includes finding the best time to give these drugs, figuring out which combinations of drugs work best, and determining how best to use these drugs with other forms of treatment.

Researchers also continue to develop new chemo drugs that might be more effective against advanced oral and oropharyngeal cancers.

In one newer approach to treating head and neck cancers, the doctor injects the drug directly into the tumor (intralesional chemo). Success with this approach has been limited in the past because the drug tended to spread out of the tumors and to nearby tissues and the rest of the body quite quickly. Recent advances in preparing the drug solution so that it remains in the tumor (such as suspending it in a gel) have renewed interest in this treatment.

New radiotherapy methods

Doctors are always looking at newer ways of focusing radiation on tumors more precisely to help them get more radiation to the tumor while limiting side effects to nearby areas. This is especially important for head and neck tumors like oral cavity and oropharyngeal cancers, where there are often many important structures very close to the tumor. With more powerful computers and newer radiation techniques, doctors are now able to plan and deliver radiation therapy more precisely than ever before.

Stereotactic radiosurgery/stereotactic radiotherapy: This type of treatment delivers a large, precise radiation dose to the tumor area in a single session (called radiosurgery, though there is no actual surgery involved) or in a few sessions (radiotherapy).

This treatment is used mostly for some brain and spinal cord tumors, but some doctors are now using it to treat recurrent oropharyngeal cancer.

Proton beam therapy: This approach uses a beam of protons rather than x-rays to kill cancer cells. Unlike x-rays, which release energy both before and after they hit their target, protons cause little damage to tissues they pass through and then release their energy after traveling a certain distance. In theory, this allows more radiation to go to the tumor with less damage to nearby normal tissues. Proton beam therapy requires highly specialized equipment and is not widely available. At this time, it is not clear that this type of radiation is any better than more standard approaches to radiation therapy (such as intensity modulated radiation therapy) in treating mouth and throat cancers.

Targeted therapy

Clinical trials are studying several targeted therapies that block the action of substances (such as growth factors and growth factor receptors) that cause head and neck cancers to grow and spread.

Several drugs that target the epidermal growth factor receptor (EGFR) may help treat oral and oropharyngeal cancers. Cetuximab (Erbitux) is already approved for use against these cancers. Other drugs now being studied include erlotinib (Tarceva®), panitumumab (Vectibix®), and lapatinib (Tykerb®).

Drugs that block the growth of blood vessels tumors need to survive, such as bevacizumab (Avastin®) and sunitinib (Sutent®), are now being studied for use against these cancers as well.

Doctors are also studying several other types of targeted drugs.

Vaccines

Most people think of vaccines as a way to prevent infectious diseases such as polio or measles. As mentioned earlier, vaccines against human papilloma virus (HPV) infection are already being used to help prevent cervical cancer. They may have the added benefit of preventing some oral cancers as well, although they won’t help treat the disease.

However, some vaccines are being studied as a way to treat people with cancer by helping their immune system recognize and attack the cancer cells. Many of these vaccines use dendritic cells (cells of the immune system), which are removed from the patient’s blood and exposed in the lab to something that makes them attack tumor cells. The dendritic cells are then injected back into the body, where they should induce other immune system cells to attack the patient’s cancer.

Gene therapy

New discoveries about how changes in the DNA of cells in the mouth and throat cause these cells to become cancerous are being applied to experimental treatments intended to reverse these changes. Gene therapies that interfere with the growth-stimulating effect of certain HPVs are also being developed. Another type of gene therapy adds new genes to the cancer cells to make them more susceptible to being killed by certain drugs. These forms of treatment are still in the earliest stages of study, so it will probably be several years before we know if any of them are effective.